1. Field of the Invention
The present invention relates generally to a communication system. More particularly, the present invention relates to an apparatus and method for transmitting data in a communication system.
2. Description of the Related Art
Intensive research on the 4th Generation (4G) communication system, or a next generation communication system, is being conducted to provide high-speed services with various Quality of Service (QoS) classes to users. More particularly, active research on the 4G communication system is being performed to support high-speed services in the way of guaranteeing mobility and QoS for a Broadband Wireless Access (BWA) communication system such as a wireless Local Area Network (LAN) system and a wireless Metropolitan Area Network (MAN) system.
A wireless channel environment in a communication system, compared to a wired channel environment, may suffer from a loss of transmission/reception data due to occurrence of an error caused by several factors such as multiple path interference, shadowing, propagation loss, time-varying noise, interference, fading and the like. The data loss acts as a factor of reducing the entire performance of the communication system. In particular, when a receiver, or mobile station (MS), of the communication system is located in an area where cells managed by a transmitter or base station (BS), from which the receiver receives a service, overlap each other, or when the receiver is located in a cell boundary, the system performance is reduced.
A description will now be made of a structure of a frame used for data transmission/reception between a transmitter and a receiver of the communication system. The communication system transmits the frame for data transmission, and the frame includes data therein, for example, a Frame Control Header (FCH), a MAP and data bursts.
The FCH and MAP transmitted over the frame are broadcast data that mobile stations will receive in common. The FCH, composed of a predetermined number of sub-channels, transfers basic information on sub-channels, ranging, and modulation schemes. A size of the MAP can be determined by parsing the FCH information.
The MAP includes data burst extraction information such as locations and sizes of data bursts in the frame, and a variety of information for providing a service to mobile stations. Therefore, by parsing the MAP information, the mobile station can extract its received data bursts in the frame.
The frame includes multiple data bursts, or normal data, and the mobile station extracts data from the data bursts based on the information acquired by parsing the MAP.
For this purpose, there is a scheme for preventing a loss of important data transmitted over the frame. To this end, a base station of the communication system transmits important data, for example the MAP of the frame, using a low modulation order, a low coding rate and repetition.
For example, when transmitting the MAP, the base station uses Quadrature Phase Shift Keying (QPSK) ½ and sets the number of repetitions to 6.
The use of the low coding rate and the repetition for the MAP data transmission can prevent the loss of the MAP. However, use of this data transmission method may cause a waste of wireless resources for actual data transmission. The waste of the wireless resources reduces the entire system performance.
Therefore, there is a need for a scheme for transmitting data so as to prevent a loss of important data in the wireless channel environment without a waste of resources to thereby prevent a reduction in the system performance in a communication system.